1. Field of the Invention
The present invention relates, generally, to a vehicle seat assembly, and more particularly to a vehicle seat assembly having a vehicle occupant sensing system and a seat cushion insert.
2. Description of the Related Art
Automotive vehicles employ seating systems that accommodate the passengers of the vehicle. The seating systems include restraint systems that are calculated to restrain and protect the occupants in the event of a collision. The primary restraint system commonly employed in most vehicles today is the seatbelt. Seatbelts usually include a lap belt and a shoulder belt extending diagonally across the occupant's torso from one end of the lap belt to a mounting structure located proximate to the occupant's opposite shoulder.
In addition, automotive vehicles may include supplemental restraint systems. The most common supplemental restraint system employed in automotive vehicles today is the inflatable airbag. In the event of a collision, the airbags are deployed as an additional means of restraining and protecting the occupants of the vehicle. Originally, the supplemental inflatable restraints (airbags) were deployed in the event of a collision, whether or not any given seat was occupied. These supplemental inflatable restraints and their associated deployment systems are expensive and over time this deployment strategy was deemed not to be cost effective. Thus, there became a recognized need in the art for a means to selectively control the deployment of the airbags such that deployment occurs only when the seat is occupied.
Partially in response to this need, vehicle safety systems have been proposed that are capable of detecting whether or not a given seat is occupied. The systems act as a switch in controlling the deployment of a corresponding air bag. If the occupant sensing device detects that a seat is unoccupied during a collision, it can prevent the corresponding air bag from deploying, thereby saving the vehicle owner the unnecessary cost of replacing the expended air bag.
Furthermore, many airbag deployment forces and speeds have generally been optimized to restrain one hundred eighty pound males because the one hundred eighty pound male represents the mean average for all types of vehicle occupants. However, the airbag deployment force and speed required to restrain a one hundred eighty pound male exceeds that which are required to restrain smaller occupants, such as some females and small children. Thus, there became a recognized need in the art for occupant sensing systems that could be used to selectively control the deployment of the airbags when a person below a predetermined weight occupies the seat.
Accordingly, other vehicle safety systems have been proposed that are capable of detecting the weight of an occupant. In one such air bag system, if the occupant's weight falls below a predetermined level, then the system can suppress the inflation of the air bag or will prevent the air bag from deploying at all. This reduces the risk of injury that the inflating air bag could otherwise cause to the smaller-sized occupant.
Also, many airbag deployment forces and speeds have generally been optimized to restrain a person sitting generally upright toward the back of the seat. However, the airbag deployment force and speed may inappropriately restrain a person sitting otherwise. Thus, there became a recognized need in the art for a way to selectively control the deployment of an airbag depending on the occupant's sitting position.
Partially in response to this need, other vehicle safety systems have been proposed that are capable of detecting the position of an occupant within a seat. For example, if the system detects that the occupant is positioned toward the front of the seat, the system will suppress the inflation of the air bag or will prevent the air bag from deploying at all. This reduces the risk of injury that the inflating air bag could otherwise cause to the occupant. It will be appreciated that these occupant sensing systems provide valuable data, allowing the vehicle safety systems to function more effectively to reduce injuries to vehicle occupants.
One necessary component common to the occupant sensing systems discussed above is a means for sensing a condition of the vehicle seat, such as whether or not the seat is occupied or whether the occupant is seated in a certain position. The sensing means is often positioned under or within the lower seat cushion, and the sensing means can include components made from a hard material. In contrast, the vehicle seat is usually filled with a soft, pliable foam cushion, and the vehicle seat is typically covered with a fabric or leather trim. Weight loading from the occupant presses the soft cushion into the hard sensing means. Over time, the cushion and possibly the trim of the vehicle seat can prematurely wear due to repeated loading from the harder material of the sensing means. This is especially true of the inboard and outboard sides of the vehicle seat because there is less foam thickness in those areas and because they bear most of the load when the occupant gets in and out of the vehicle. Once the foam of the seat cushion begins to wear, the occupant is more likely to feel the sensing means through the cushion, and this can make sitting on the vehicle seat uncomfortable. Accordingly, there is an ongoing need in the art for a vehicle seat assembly that is reinforced to inhibit premature wear and discomfort caused by the sensing means positioned within the seat assembly.
Moreover, the lower seat cushion is typically a uniform foam piece. Weight from the occupant of the seat cushion deflects the uniform foam piece into the sensing means in some occupant sensing systems, thereby causing a response from the sensing means indicative of the presence of the occupant. An example of such a system can be found in the published patent application having U.S. Ser. No. 10/249,527 and Publication No. US2003/0196495 A1 filed in the name of Saunders et al. In these systems the seat cushion foam exhibits certain material characteristics, such as density, indentation load deflection (ILD), and the like, that affect the response of the sensing means. For instance, a seat cushion with denser foam may deflect less and transfer less load from the occupant to the sensing means in comparison to a seat cushion with less dense foam. In that example, the sensing means associated with the denser foam might detect less load from the occupant as compared with the sensing means associated with the less dense foam. Thus, the response of the sensing means can be related to the material characteristics of the foam in the seat cushion.
Although vehicle seat assemblies with uniform lower seat cushions have generally worked for their intended purposes, problems still remain. For instance, the load bearing characteristics of the seat cushion may need to be changed, for instance, to meet changes in cushion requirements or to vary the response of the sensing means. The entire uniform seat cushion can be replaced, but this adds unnecessary cost and time to the assembly of the vehicle seat assembly. Accordingly, there is an ongoing need in the art for a vehicle seat assembly in which the load bearing characteristics of the seat cushion that can be changed more easily and at lower cost.
Furthermore, voids can develop in the seat foam during its manufacture. Gas bubbles move through the mold used to create the seat cushion. As the foam material cures, the bubbles settle—usually at the outer surfaces—and create voids. The voids can detrimentally affect the response of the sensing means. If the outer surfaces of the seat foam are curved, the bubbles typically congregate near those surfaces. The resultant voids exacerbate the detrimental effect on the response of the sensing means. Accordingly, there is also an ongoing need in the art for a vehicle seat assembly with a seat cushion design less likely to develop a congregation of voids during manufacture such that the associated sensing means can respond more accurately in detecting the presence of an occupant.